ThO2—W thermionic cathodes, as the key part of the vacuum tubes, are widely used for many fields, such as microwave oven. However, ThO2 is a radioactive substance and ThO2—W thermionic cathode has poor ductility and low yield (˜60%), which cause problems in the manufacturing and application of the cathodes. Therefore, it is essential to find out substantial materials.
La2O3 and Lu2O3 co-doped Mo filament cathode was fabricated by liquid-liquid (L-L) doping method. The mixed powders prepared by this method dispersed uniformly which can improve the emission homogeneity and emission stability. The cathode fabricated by L-L doping method can be operated with high temperature carbonization treatment and out-gassing treatment, these treatments are important to the emission stability of the cathode applied to the magnetrons. Study [Y2O3—Lu2O3 co-doped molybdenum secondary emission material, Yang, Fan; Wang, Jinshu; Liu, Wei; Liu, Xiang; Zhou, Meiling, APPLIED SURFACE SCIENCE, 270(746-750), 2013.] has shown that Y2O3—Lu2O3 doped Mo cermet cathodes possess higher secondary electron emission properties than Y2O3—Mo cathode. It means that adding Lu2O3 can improve the secondary electron emission properties of Y2O3—Mo cathode. La2O3—Mo cathode cannot be applied to magnetrons due to its poor emission stability, because there was no continuous supplement of electrons when this cathode was working. Since Lu2O3 can improve the secondary emission property of cathode, adding Lu2O3 into La2O3—Mo cathode may maintain the supplement of electrons when the La2O3—Mo cathode was working. Therefore, this patent added Lu2O3 and La2O3 into Mo powder to make La2O3 and Lu2O3 co-doped Mo filament cathode. This composition has not been reported by previous researches.
The present invention provides a method of carburization treatment of the La2O3 and Lu2O3 co-doped Mo filament cathode. The temperature of carburization of the present invention is much higher than the previous researchers, and the carburization time is short. The carburization degree of the present invention is high (about 10-50%). Therefore, there remains a further study of rare earth oxides doped Mo cathode used for magnetrons applied to microwave emitter equipment, especially for microwave oven.